Indicating and control apparatus for radio receivers



P 4 w. L. DUNN ETAL 2,256,668

INDICATING AND CONTROL APPARATUS FOR RADIO RECEIVERS Filed April 25, 1938 3 Sheets-Sheet l p 1941- w. L. DUNN ETAL 2,256,668

INDICATING AND CONTROL APPARATUS FOR RADIO RECEIVERS Filed April 25, 1958 3 Sheets-Sheet 2 F 0! /V 720/ azaiz r 62 Sept. 23, 1941. w DUNN ETAL 2,256,668

I INDICATING AND CONTROL APPARATUS FOR RADIO RECEIVERS Filed April 25, 1938 3 Sheets-Sheet 3 @"Wm u Q Patented Sept. 23, 1941 INDICATING AND CONTROL APPARATUS FOR RADIO RECEIVERS William L. Dunn, Richard C. Mal-hols, and Alexander W. Piensler, Chicago, 111., more to Belmont Radio Corporation, Chicago, 111.,1. corporation of Illinois Application April 25, 1938, Serial No. 204,032

7 Claims.

Our invention relates in general to radio control and indicating apparatus, and more in par-, ticular to a demountable self-contained unit for controlling the operation of an automobile radio receiver from a position spaced from said re-- celver and indicating the controlled positions of the receiver. Such controlling includes the changing of the resonance frequency of the auto-- mobile radio receiver circuits by manually op'er ated predetermined station selector mechanism in the unit itself.

It has been the general practice with automobile radio receivers to mount the receiver on the fire wall of the automobile, or an adjacent loca tion, and control the variable condenser or other frequency changing means within the radio receiver to tune the receiver from a control head mounted on the dash board or steering column and connected to the radio receiver by means of flexible mechanical cables. The volume control has normally been mounted in the radio receiver 1 itself and has likewise been operated from the control head. In addition, the head has normally been provided with a dial scale or the like to indicate the ituned position of the radio receiver. This structure has always presented difliculties in constructing and mounting the two parts of the complete radio receiver system in a manner so that there would be no kinks in the flexible cables intermediate the same, and so that the control members would operate easily with a minimum of back lash to ,provide relatively simple and accurate tuning. Although improvements have been made in the control heads and in the connecting mechanical cables so that relatively satisfactory tuning was accomplished, such results were attained only with relatively expensive, and in some respects complicated structure.

In an elfort to eliminate the constructional difficulties and expense of the mechanically conone of the two types of prior constructions when attempting to use mechanically operated automatic operated automatic tuning with the automobile radio receiver. Mechanically operated automatic tuning structure for the control head is extremely unsatisfactory, if operable at all because of the frictional losses in the flexible cables intermediate 3. control head and a radio receiver. Adding mechanically operated automatic tuning elements to the single housing receiver including the control portion, as discussed above, normally adds still further to the bulkiness of the same. Although electrically operated automatic tuning solves the problem with respect to the flexible cable connections, electrical automatic tuning, as now practiced, is expensive, and as a result can be used only on the higher priced radio receivers.

An object of our invention is to provide an improved self-contained control and indicating unit for an automobile radio receiver, remotely spaced from receiver chassis and housing.

It is also an object of our invention to provide a single demountable, self-contained compact unit fornot only controlling the tuning and other operations for an automobile radio receiver from a remote position, but actually changing'the resonance frequency of the receiver 7 circuits all at such remote position, with only an electrical cable connecting such unit and the receiver proper including the tubes.

A further object of our invention is to provide manually operated automatic tuning for an automobile radio receiver in a control head spaced from the radio receiver itself and connected thereto only by electrical conductors, with the control head adaptedfor ready mounting on the nected units, there has also been some use in the receiver in any place other than the dash board normally makes it inaccessible to the operator.

A further problem is presented with either dashboard of an automobile in a manner substantially as simple as the mounting of the usual control head of the prior art.

One of the features of our invention is the provision of a self-contained control unit for an automobile radio receiver in which predetermined station settings can be eifected simply and easily without the use of tools, and the receiver then operated from such unit so that the resonance frequency for the receiver circuits is changed directly at the unit and the desired resonance,

frequency is then maintained accurately in spite of the jarring and generally rough movements to which an automobile radio receiver is subjected. Other objects, features and advantages of our invention will be apparent from the following description taken with the drawings in which:

Fig.4 is a perspective view of the complete control and indicating unit illustrated with a bracket for mounting the same in an appropriate position on an automobile.

Fig. 2 is a plan view of the unit with the top of the housing and end members cut away to expose the inside portions of such unit.

Fig. 3 is a fragmentary detailed view of the gear mechanism intermediate the rotary driven shaft and the indicating mechanism in the unit along the line 3-3 of Fig. 2.

Fig. 4 is a fragmentary detailed view of the pinion from the manual control knob and the crown gear for the rotary shaft in engagement therewith.

Fig. 5 is a sectional view along the lines 55 of Fig. 2 on a reduced scale as compared with Fi 2.

Fig. 6 is a diagram circuit for the control and indicating unit.

Fig. 7 is a rear elevational view of the unit with the rear housing portion cut away.

Fig. 8 is a modification of the core moving mechanism for the variable inductance members.

In the illustrated embodiment of our invention, a box-like housing I0 is provided normally open at each end, but closedin thecomplete unit by means of a cap II at the rear and an escutcheon plate l2 at the, front thereof. The unit is entirely self-contained, and may be mounted on the dash board or the like of an automobile by means of a stamped bracket l3 having a plurality of apertures I4 therein. The bracket is first mounted on the automobile and the unit then removably supported therefrom by doubl ended bolts 16 on the unit which are slidably inserted into the four notches I! on the side walls of the bracket. Suitable means may be provided for locking the control unit onto the bracket. The radio receiver which is operated Each inductance unit may be considered as having a substantially fixed member, as the coil 21, for instance, and an interleaving movable member, or metal core, as will be described. One end of the tube 26 is supported at the plate 28 of insulating material by means of a formed fiber dowel cup eyeleted to the plate. The plate 28 in turn is supported in corresponding recesses in opposite sidewallsof the can. The opposite end of the tube 26 is supported at an end aperture 33 in the can 24 and projects through an elongated notch correspondingly positioned with said aperture in the back portion of the U-shaped principal frame member 34. The three coil units are each supported at the back by two threaded spade bolts 29 for each unit extending through the back panel 30 of a one-piece frame plate 3| which extends over the top of the cans and is secured at a vertical flange 32 to the back portion of the frame member 34.

The inductance of the coil is varied by moving therethrough a core 36 having suitable magnetic properties including an effective permeability greater than unity, by means of a cord or cable arrangement with one piece of the cord 31 tied to an eyelet in one end of the core and passing over a. suitable pulley on a rotary shaft as will be more fully described hereinafter, while a second piece of cord 38 is secured to the opp site nd of the core in the same manner and passes over a pulley 39 secured to a rotary shaft from the control unit is independently supported at a suitabl place on the automobile normally remotely spaced from the control unit, and the sole connection between the control unit and the radio receiver is made by the conductors enclosed in a braided covering 18 to form a cable, and having a suitable connecting member I9 at the outer end thereof. A pair of conductors 2| extend out of the housing l0, one of such conductors being suitably connected to the ungrounded six (6) volt connection for the receiver chassis itself, and the other making connection with the storage battery for the automobile or other source of A current for the control unit and the receiver. A receptacle 22 is provided at the back of the unit frame as shown in Figs. 2 and 7. The lead from the antenna appropriately mounted on the automobile is connected into this receptacle. The cable I8 and the three conductors just mentioned are the only connecting means of any type extending to the control unit, and from the control unit to the radio receiver.

As stated above, the present invention provides manually operated automatic tuning foran automobile radio receiver without the use of any mechanical connection between the automatic tuning apparatus and the radio receiver itself spaced from such apparatus. This is accomplished by means including three variable inductance coil units 23 with each of such units including an open-ended coil can 24 having rigidly supported therein a variable inductance including an elongated tube-26 of insulating mabetween each cord member 37 and 38 as shown in Figs. 2 and 5.

An automobile radio receiver is inherently subject to a great deal of vibration and the usual variable or gang condenser previously employed was susceptible to detuning because mechanically it is unbalanced. Therotors in one tuning position acting under the force of gravity and vibration tend to move away from that tuned position. In the resonance frequency changing means in the control unit of our invention as described above, the tubes 26 for the coil units are mounted (Figs. 5 and 7) so that the metal cores 36 move substantially in a horizontal direction and the force of gravity will have little effect in changing the set position thereof. The slight angular displacement of the tubes from the horizontal is still less than the critical angle of friction or slip angle for the cores 36, and in exhaustive road tests on the commercial embodiment of our invention, we have found that the angle, as shown in Figs. 5 and 8, in shielding cans 24 so as to reduce the overall-length of the unit as much as possible. A line drawn longitudinally nected into the antenna circuit, the oscillator cirterial having wound thereon a coil 21 having a specific inductance value corresponding to recult, and the RF or converter tube circuit, respectively, of the radio receiver controlled by the unit. The corresponding cords or cables for the cores-of these coils ,ar looped around pulleys 41, 48, and 49, respectively. The pulleys .41 and 49 are preferably floating on a rotary cam shaft non-rotatably keyed to the rotary shaft II which is Journalled in a pair of identical frame brackets 62 and these in turn are rigidly secured to the frame member 36. The pulleys 38, as previously described, are all preferably rigidly secured in the shaft or axis means 6| so that the cable over the pulley' 68 and its corresponding pulley 36 drives th shaft 6| and the latter carries the other two pulleys 36 therewith to maintain the cores 36 in alignment with one another as will be more fully explained. It is understood, however, that the three pulleys 61 to 69 may all be keyed in the shaft against rotation relative thereto and all cores driven from these pulleys while pulleys 36 on shaft 6| act as idler pulleys.

The shaft 5| may be rotated by means of selected cams in the manually operated automatic tuning portion of the control head, or by the man- -ually operated knob 56 on the outside of the escutcheon plate II. The latter is secured to a stud shaft having a pinion gear 56 on the inner end thereof. This gear engages a crown gear 56 (Fig. 4) which is relatively thin and flexible to permit an over-running as between the pinion gear and itself at the end of a tuning stroke, as will be described. The crown gear 56 is normally rotatable with reference to the cam shaft 5| upon which it is supported, as well as longitudinally slidable thereon. Rotation with reference to the shaft, however, is prevented by means of a locking arm 51 keyed to the shaft 5| and having a projection 58 inserted into an elongated aperture 59 in the crown gear, elongatedso that lateral flexible movement of the crown gear is permitted, but narrow enough that the aperture flts rather snuglyover the pin 58 so that there will be little or no angular play as between the pin 58 and aperture 59. The crown gear is pressed outwardly against a washer 6| retained on the shaft by a threaded nut 62, by means of a spring washer 53 pressing against the inside face of the crown gear at the shaft 5|. The spring washer 63 keeps the crown gear always in complete engagement with pinion 56, thereby preventing backlash as between these two members, and in turn, the control and indicating portions of the unit, even though the crown gear 56 may be somewhat eccentric on shaft 5| or may depart somewhat from flatness. The angular movement of the arm 51 is limited to approximately "180 by the pair of lugs 66 oppositely disposed,

and stamped out of the frame bracket 52 in the line,of,movement of such arm. When the-arm 51 engages one of the stop lugs 66, further movement of the shaft 5| and crown gear 56 thereon is stopped. To prevent inJury to, or displacement in the stop mechanism and consequently injury to the tuning mechanism, the crown gear 56 will pushing of a button corresponding to the desired station position. In the present embodiment of the invention, such automatic tuning is accomplished by means of a plurality of heart-shaped cams 66, suppo t d on shaft 6| for rotational and longitudinal movement relative thereto, but normally retained rigidly on such shaft under frictional pressure. The cams 66 are spaced apart by means of collars 61 of various widths, as can be seen in Fig. 2, and each cam is normally retained against rotation by frictional washers 68 keyed against rotation on the shaft 5| but longitudinally slidable, and abutting ea'ch cam 66 on each side thereof. The frictional pressure on the cams is varied by means of a thumb screw 69 protruding from the housing l6, threadably secured on the end of the shaft 5| and bearing against the longitudinally movable assembly on such shaft, including the collars, cams, washers and pulleys. This structure has been more particularly described and claimed in copending application Serial No. 170,070 filed October 20, 1937, but it might be explained briefly in the present application, however, that this frictional pressure is reduced by first rotating the shaft in the properdirection by means of the thumb screw 69 or the knob 53 until the arm 51 engages a lug 66. The shaft 5| can turn no further and the thumb-screw 69 is then unscrewed thereon. With the frictional pressure on each cam reduced sumciently it may be adjusted relative to the shaft 5| by holding it with a selector lever, as will be described, while the shaft 5| is rotated independently by means of the control knob 53. When the cams are adjusted to the predetermined position for automatically selecting a desired station setting, the thumb screw may be screwed onto the shaft 5| to move the assembly as described, and when it becomes tight enough so that the shaft will turn therewith, the shaft is rotated until it engages the opposite stop lug 66 in which position the thumb-screw may be tightened down to provide the desired frictional pressure on the cams.

The cams 66 are selectively rotated to thereby 45 rotate the shaft 5| to a predetermined angular 16 thereof. A split extension TI on the front of the front leg 16 is adapted to frictionally engage the inside wall of a cavity in a molded button 18, which button is further retained in place by a frictional locking connection between notches in the extension 11 and slight projections on the ances-can be moved as the result of rotation of the shaft by the knob 53, and thus set to any tun'ed position as indicated on the dial for the unit, such knob is employed primarily for setting or resetting the control members of the automatic tuning portion of the unit to predetermined tuned positions. Thedesired predetermined station setting can then be obtained by the mere inside of the cavity. The levers II are spaced apart on the shaft or bar 12 by dropping them in annular recesses I! in the bar so that each lever is supported on a restricted neck of the bar at the notch 13 as shown in Fig. 5; Each lever is retained in place upon the rod 12 by means of a hair-pin spring 16 having one end 8| hooked over the back of the leg 16 of the lever and extending therefrom under the rod 12 to be hooked over the top edge of the front leg 16 and then extend downwardly to lay against a stationary pin 65, Two of such pins are provided, each supported at its outer end from a frame bracket 52 (Fig. 2), and the two spaced far enough apart at their inner ends to permit the rotation of a drum-type dial therebetween. The pins serve 7 a double function inasmuch as they act not only as a stop for the front extension of the wire on one side, but also as a stop for the leg 16 of each lever on the other side (Fig. 5). The spring furthermore, acts not only to retain the lever on theshaft 12, but also as a tension and return spring as is readily apparent. A roller 86 on the end of each lever engages a periphery of a corresponding cam 66 and moves the latter until such roller is seated in the depression 81 of the cam. At'this position of the selected lever and cam, the cores 86 within the three inductance coils have been moved'in unison to a position such that the inductance values of the coils efl'ect a tuning or resonance frequency adjustment in their respective circuits in the radio receiver to tune the receiver as a whole to its predetermined station setting. The tuned position is indicated on the dial of the indicating portion of the unit and may be specifically pointed out by station identification, on tabs, T removably secured in apertures above each of the selector levers as shown ,in Fig. l.

Each cam 66 is set to a predetermined position relative to the shaft 5| by holding the cam stationary with the roller 86 of the selected lever corresponding to that cam seated'in the depression 81 of the cam. With the friction reduced or removed as above described the shaft 5| is rotated by the knob 53 to attain the desired angular position relative to the cam.

The mephanism for indicating the angular position of the shaft 6| and thereby the tuned position of the radio receiver connected with the control unit, includes a drum-type dial with a scale plate 88 supported on a disc 89 which in turn is rigidly secured to a sleeve or bushing 9i by the plates 96, and in engagement with the gear teeth by meansof guide means including a tension pulley 98 appropriately mounted 'below the rack on axis means X and engaging the same on a line between the centers of the gear 86 and pulley 86, which line is substantially at right rotatably mounted upon the shaft 12. The dial assembly on the sleeve 9| is rotatable as well as longitudinally slidable on the stationary shaft 12, and is maintained substantially in a single longitudinal position on such shaft by means of 'a gear 92 positioned intermediate apair of discs driven gear structure which includes a toothed 93 which are of a greater diameter than, the

driving gear 94 is keyed to the shaft 5| and maintained intermediate the-sleeves 61 on each'side thereof, as previously described. The extending v edges on the discs 93 for the driven gear define the lateral movement of the sleeve 9|, to which the elements of the assembly are rigidly secured, relative to the driving gear 94 so that the entire dial assembly is maintained in proper alignment on the stationary shaft 12 in the control unit.

A modification of. the moving mechanism for the cores 36 in the inductance coil units is illustrated in Fig. 8. Instead of using the multiple pulley and cable mechanism for each unit as illustrated particularly in Fig. 5, a toothed rack 95 is'employed, secured to a core 36, anddriven by a gear or connector 96 on the shaft 5|. The rack 95 is preferably provided in an insulating material so that the range or electric properties of the coils will not be affected by its connection with the core and its movement in the tube. The driving gear unit is similar to that illustrated in Fig. 3, with a guide plate 96' on each side of the gear 96 and extending beyond the periphery of the gear, and all three elements secured to a bushing 91 which is keyed to the shaft 5|. The toothed rack is maintained in the channel formed angles to the path of movement of the rack. The axis or axis means X in turn is supported upon a spring tensioned pivoted arm Y, and yieldably movable toward and away from the rack. The arm Y is mounted at Z for pivotal movement abouta axial center. The gear 96 assembly is friction y held on the shaft 5| in addition to the keyin described, by means of friction washers as 68 for the cams 66. A corresponding structure is, of course, provided for each of the coil units. This modification eliminates the pulleys at the rear of the control unit and thus makes it possible to decrease the overall length of such control unit. In addition, such core moving or driving means provides a rigid assembly which may be very quickly and simply assembled into the unit. It is, of course, necessary to originally align the cores of the three units, and such align-. ing operation is made extremely simple with this mechanism as the rack 'may merely be moved tooth by tooth one way or the other relative to the corresponding gear 96 until the alignment is attained.

As to the circuit for the control head, as illustrated in Fig. 6, the signal generated in the automobile antenna connected through the socket 22 at the rear of the unit passes through spark noise filter coil lllimounted on the insulating panel at the back of the unit adjacent the socket as shown in Fig. 3 and is impressed upon variable coupling capacity M12. The capacity 992 is variable in order to compensate for difierent sizes of antennas that might be used with the receiver system as well as variations in circuits due to individual changes in the capacities of tubes, cables and the like in the receiver system. The spark filter coil I0! in combination with a spark plate condenser I83 and coupling-capacity J82 constitutes a low pass filter to filter out all disturbances lying outside the regular broadcast band which is resonant on the antenna for the receiver. The variable inductance coil in the antenna circuit is, of course, the left handcoil in the control unit as viewed in Fig. 2. For purposes of clarity, in the circuit diagram of Fig. 6, such coil unit 23 is designated by the words Ant. Coil. The coil Ant. Coil is connected across the coupling capacity I02, and connection with the corresponding tube in the radio receiver is accomplished by an individually shielded, low capacity conductor Hi l in the cable 89. The coil.

Ant. Coil and its corresponding tube in the receiver are elements in a tuned circuit, the resonant frequency of which may be varied by varying the inductance of the coil. This, of course, is

such inductance coil is consequently carried on the shaft 5| adjacent the driving gear 94 with merely a sleeve 61 intermediate the two. The inductance value of the coil, as the result of the position of the core 36 therein, is very critical in the tuned circuit for such coil. Although the tolerances permitted between-the lug L of each pulley, and the 'keyway K in the shaft 5i are very small, a very slight angular deviation at the shaft is considerably larger at the circumference of the pulley where the driving cable for the core is carried. It is understood, of course, that the friction is removed or applied to all of the control cams 66 on the shaft BI simultaneously, and they may all be set to a predetermined control position one after another, all while the friction is continuously removed. The shaft BI is rotated while each cam 66 is being set, and the pulley 48 rotated with the shaft. To prevent undesirable angular displacement of the pulley 48 with reference to the shaft while the friction is removed, a take-up spring I" is carried on the sleeve 61 with one end of the spring hooked into a tooth of the driving gear 94 and the other end hooked into an eyelet I" of the pulley 48. With this anchoring of both ends of the coil spring, the tension is in a direction such as to hold the lug L against one side of the key way K so that it remains in this position both when the friction is applied and when it is removed from the cam.

The oscillator coil OSC is in series with a coil I09 and a trimmer condenser III) is connected in parallel with the two coils and intermediate the individually shielded, low capacity lead III, for one side of coil OSC," and ground. The lead III extends from the other side of the coil CS0 to the corresponding tube circuit in the radio receiver.

The antenna and R. F. inductances in our embodiment of the invention cover a range of frequencies from 540 to 1560 k. c. This is a ratio of approximately 2.9 to 1. The oscillator inductance on the other hand covers a range from 1005 k. c. to 2025 k, c. which is a ratio of approximately 2.04 to 1. It is necessary, therefore, to make less of the inductance coil variable than with the other two units, and this is accomplished by the use of the non-variable inductance I09 in series with the coil 080 as described above in the control unit, and in addition, the use of fixed inductances in the radio receiver proper shunted across the two coils. The series coil I09, may, however, be omitted entirely by making the form factor of the coil OSC" different from that of the other two coils "Ant. Coil and "R. F.

A third variablev inductance unit includes a coil and movable core for connection into the circuit of the first R. F. tube in the radio receiver and for convenience this coil unit will be designated on the circuit diagram of Fig. 6 as "R. F.

thelr respective circuits in the receiver system including the present control unit. I A pair of conductors H3 and H4 connected with opposite ends of the coil R. F. are carried in the cable It for connection to the corresponding circuit portionin the radio receiver. Conductor H4 is individually shielded 'in the same manner as conductors I04, and III, and-similar to these conductors, has as low a capacity as possible. These three conductors are individually shielded in the shielded cable I8, to prevent any reaction between the three, and also to provide the maximum protection against pickup of electrical fields caused by motor noise. It is unnecessary to individually shield conductor H3 because this is bypassed to ground immediately upon its entrance into the radio receiver.

Not only is the resonance frequency changing itself accomplished in the control unit, but a tone control, volume control, and sensitivity control for the radio receiver circuit are provided at least as to their mechanical portions in the control unit for operation from the front thereof. A suitable volume control unit H6 is mounted from one of the frame brackets 52 with a rotatable shaft extending forwardly to receive a control knob H5 at the front of the escutcheon plate I2. As illustrated in the circuit diagram of Fig. 6, this includes a resistance unit with conductors H1 and H8 connected from opposite ends thereof and extending to the radio receiver. A variable contact point I I9 is likewise connected by a conductor I20 with the radio receiver circuit. The volume control leads I" and I20 are carried together and shielded as a pair to prevent any undesirable reaction with the radio frequency leads previously described, and also to prevent their pickup of motor noise; A sensitivity switch I2I is operable from the front of the escutcheon plate I2 and acts through suitable electrical means in the radio receiver to which it is connected by conductor I2I' to provide the maximum sensitivity for such receiver on distant stations and reduce sensitivity on local stations. Leads on conductors Ill, and HI are individually bypassed to ground immediately upon their entrance into the radio receiver, as described for lead I I3. The tone control switch I22 is connected into the volume control and tone control network as shown, and such network is connected to the radio receiver to emphasize the low notes or high notes as desired, in the reproduction of the signals picked up by the antenna.

The current supply to the control unit as well as to the radio receiver itself is introduced by one of the leads 2| as previously described with an on and oil switch I24 in the circuit to turn the control unit and radio receiver on and of! so far as electrical energization is concerned. The switch I24 is mounted at the volume control and operated by the knob II5. A pilot light I26 for illuminating the dial scale 88 is also connected into the current supply line on one side while the other side is grounded through the ground connection common to the coil OSC," and the antenna coil Ant. Coil," as well as the sensitivity switch I2I. To satisfactorily shield all of the conductors in the 'cable I8, and double-shield conductors such as I04, III, H4, H1, and I24, a metal braided cover I21, illustrated diagrammatically by dotted lines in Fig. 6, surrounds the conductors in the cable and is appropriately grounded to the housing or frame of the control unit at bracket I28 (Fig. 7) where the cable extends through an aperture for support on the unit.

From the above description it is apparent that we provide a compact, sturdy demountable indicating and control unit for an automobile radio receiver from which unit resonance frequency changes in the tuned circuits of the radio system can be accomplished automatically by manually and mechanically operated means. After the predetermined station settings for the control'cams of the unit are effected, any station may be tuned in simply by depressing a button 18 on the corresponding lever to move the three cores 2 in the variable inductance units in unison, to simultaneously bring the inductance of the coils 21 to a value such that resonance is accomplished in the coil circuits and corresponding tube circuits for each coil in the radio receiver proper. Ini- 6 V tial setting of the cams can be completed without the use of any tools and without getting into the control unit proper. Complete control of the unit and the radio receiver itselfmay be accomplished entirely from the front of the esand sturdy. The control unit itself is small enough to occupy only a relatively small space on the dash board of the automobile, and as can be seen from Fig. 1, presents a very pleasing and attractive appearance to the operator. Automatic tuning for an automobile radio receiver is thus provided at very low cost with none of the objectionable difiiculties with prior movable mechanical connections to the radio receiver as originally discussed.

Although we have described our invention in its preferred embodiments, it is understood that the invention is not limited thereto, but changes and modifications may be made therein, all within the scope of the appended claims.

We claim:

1. Radio tuning means including a plurality of inductance coil units with each of said coil units including a movable core, driving means for said cores including a rotary shaft, a driving pulley on said shaft maintained against rotation relative thereto, a second rotary shaft, a plurality of pulleys on said second shaft with one of said pulleys corresponding to said driving pulley and all of said second shaft pulleys normally retained against rotation relative thereto, a flexible connecting means between said driving pulley and said one pulley, additional pulleys on said first shaft normally rotatable relative to said first shaft corresponding in number to the second shaft pulleys other than said one pulley, flexible connecting means between each of said additional pulleys and a corresponding other pulley, with each of said flexible means connected to a movable core, and with said cores being movable in unison upon rotation of said second shaft when driven by rotation of said first shaft, and means for minimizing play between said first shaft and the driving pulley.

2. Radio tuning apparatus including in combination, a rotary shaft, a plurality of operating units each operating in a direction substantially at right angles to said shaft, each operating unit including a push button at the front end thereof, a control member on said shaft and means operatively connecting said push button and said control member, and a plurality of inductance tuning units, each inductance tuning unit including a movable core and a substantially fixed coil assembly having a coil and a form therefor, with all of said coil forms positioned substantially longitudinally with reference to said operating units, and one end of each of the coil forms extending into the region of the back ends of the operating units, coupling means operatively connecting each movable core and said shaft having a portion mounted on said shaft with said portions being interspersed in an axial direction on said shaft relative to said control members, and at least a portion of said coupling means and cores and said operating units being interspersed in said apparatus in a direction corresponding to said axial direction in the position of maximum displacement of said cores relative to the fixed coil assembly.

aaaaees 3. Radio tuning apparatus including in combination, a rotary shaft, a plurality of operating units each operating in a direction substantially at right angles to said shaft, each operating unit including a push button at the front end thereof, a control member on said shaft, and means OD- eratively connecting said push button and said control member, and a plurality of inductance tuning units extending substantially longitudinally relative to said operating units, each inductance tuning unit including a movable core, a substantially fixed coil assembly having a coil and a form therefor, and coupling means operatively connecting each movable core and said shaft having a portion mounted on said shaft with said portions being interspersed in an axial direction on said shaft relative to said control members, and with one end of each of said coil forms extending into the region of the back ends of said operating units and being interspersed in said apparatus relative to said operating units in' a direction corresponding to said axial direction, and shielding means for the assemblies, with one end of the shielding means positioned adjacent the back ends of the operating units.

4. Radio tuning apparatus including in combination a rotary shaft, a plurality of operating units operating in a direction substantially at right angles to said shaft, each operating unit including a push button, a control member on said shaft and means operatively connecting said push button and said control member, and a plurality of inductance tuning units spaced longitudinally from said shaft with each such unit including a fixed coil assembly and a movable core, with the core moving in a direction substantially at right angles to said shaft and all said coil assemblies positioned substantially longitudinally with reference to said operating units, with each inductance tuning unit also including driving means on said shaft, and connecting meas intermediate each movable core and a corresponding driving means, with said driving means and said control members being inter spersed axially on said shaft, and said connecting means and said push-button-operatively-connecting means being likewise interspersed in a direction in the complete apparatus corresponding to the axial direction of the shaft and each said last two-mentioned means operating in generally longitudinally extending paths of movement, with such paths of movement for said connecting means being overlapping in a longitudinal direction as to such pathsof movement for said push-button-operatively-connecting means but with the spacing in an axial direction being such that each unit moves unobstructively with reference to the other units, with said connecting means for said inductance tuning units having a portion in at least one position extending toward said push buttons and beyond the rotary shaft in the direction toward said push buttons, and with such previously defined arrangement providing an easily operated apparatus and an apparatus which is compact in a longitudinal directionfrom one end to the other thereof.

5. Radio tuning apparatus having frame means and including in combination a rotary tuning shaft supported by said frame means and extending transversely thereof, a plurality of push buttons at the front of said frame means, a plurality of inductance tuning units longitudinally spaced from said shaft toward the back of aid frame means, a plurality of control members on said shaft corresponding in number to said push buttons, means operatively connecting said push buttons and said control members to rotate said shaft, a plurality of driving members on said shaft interspersed thereon with said control members, with each of said inductance units including a fixed coil assembly and a movable core, connecting means operatively connecting each movable core and its corresponding driving member and operating in a substantially longitudinal path of movement, and with said inductance units positioned substantially adjacent said control members in a longitudinal direction and said connecting means and core for each such unit movable in a path intermediate two adjacent control members so as to utilize the axially extending space intermediate said control members and provide the tuning apparatus as compact as possible from front to back thereof.

6. Radio tuning apparatus including in combination a rotary shaft, a plurality of operating units each operating in a direction substantially at right angles to said shaft, each operating unit including a push button at the front end thereof, a control member on said shaft and means operatively connecting said push button and said control member, and a plurality of inductance tuning units extending substantially longitudinally relative to said operating units, each inductance tuning unit including a movable core, a substantially fixed coil assembly having a coil and a form therefor, coupling means operatively connecting each movable core and said shaft,

of said coil forms being interspersed in said apparatus relative to said operating units in a direction corresponding to said axial direction, and shielding means for the assemblies, with one end of the shielding means positioned adjacent the back ends of the operating units.

7. Tuning mechanism for radio apparatus including in combination a plurality of operating means and each including a push-button, a plurality of inductance coil units spaced longitudinally from said operating means, and a rotary shaft intermediate said operating means and said inductance coil units and extending transversely thereof, a plurality of control members on said shaft spaced apart axially thereon, means operatively and selectively connecting said operating means and said control members, each of said inductance coil units including a coil assembly and a core movable therein with one end of each unit adjacent the control members on the rotary shaft but spaced longitudinally therefrom with the cores movable toward and away from said shaft, driving means on said shaft corresponding to each inductance coil unit, link means for each coil unit operatively connecting the movable core and. the corresponding driving means, with the plurality of driving means and the plurality of control members interspersed on the shaft and a link means and corresponding core for each coil unit movable in a space intermediate two adjacent control members, with said link means at one position of movement having a portion thereof extending forwardly toward the push buttons beyond the transversely extending rotary shaft to utilize the space between said control members for longitudinal movement of the link means and core and provide the tuning mechanism oompact in a longitudinal direction.

WILLIAM L. DUNN. RICHARD C. MARHOLZ. 

